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  #46  
Old 07-01-2016, 09:42 PM
phavriluk phavriluk is offline
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I had a headstock veneer delaminate in one corner from the neck on my two-year-old Taylor GS Mini. Taking advantage of Taylor's lifetime guarantee to the original owner, I sent the guitar to the Taylor mother ship for attention. Attention I got. A new neck and new strings. Easier for Taylor to swap the neck than do workbench repairs on my neck and send it back to me. Sure makes for a happy customer. One person's opinion about Taylor's NT neck.
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  #47  
Old 07-02-2016, 04:06 PM
Tom West Tom West is offline
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Originally Posted by Bruce Sexauer View Post
Here's an interesting bit of related trivia. We all know that steel string guitar tension is in the neighborhood of 150 lb in line with the neck, and I think that is true though I haven't measured it. What is interesting is that those who do measure things tell me that this translates into a mere 4 lb +/- of pressure perpendicular to the strings at the nut. Since the neck is just over 12" long, and the heel is just over 3" long, we can see that the lever the neck represents produces just 16 lb (4X) of pressure away from the body at the heel cap. These are not very big forces IMO, though they are constant. This is also an incentive to keep the set up on your guitar in good health, as it does not take a much higher action to double the 4 lb figure.
Not so sure of that Bruce..............!!
Tom
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  #48  
Old 07-02-2016, 04:37 PM
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Not so sure of that Bruce..............!!
Tom
If you think my numbers are off, Tom, I'd like to know what you think is true.
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  #49  
Old 07-02-2016, 05:34 PM
Tom West Tom West is offline
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Bruce:
I would think it is closer to 150 divided by 4,resulting in about 37.5 lbs minus what ever the offset for the nut is. No engineer here so maybe one can jump in and help.
Tom
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  #50  
Old 07-02-2016, 05:39 PM
JoeCharter JoeCharter is offline
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[sorry - will do my math when I have time and edit my comment]

Last edited by JoeCharter; 07-02-2016 at 05:49 PM.
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  #51  
Old 07-02-2016, 05:40 PM
Tom West Tom West is offline
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Bruce:
With sober second thought, what I have said would be valid if the pull is perpendicular to the fingerboard. Engineers...........??
Tom
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  #52  
Old 07-02-2016, 05:49 PM
Tom West Tom West is offline
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Bruce: Starting to feel stupid, If 150 lbs. was perpendicular to neck, the force away from heel would be 150 x 4=600 lbs. Time for me to tuck tail and go home. Tongue engaged before brain gets one in trouble. In other words you are most likely right.
Tom
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  #53  
Old 07-02-2016, 05:57 PM
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Here's my very unscientific opinion. I can double the action on my acoustic by pushing the neck pretty lightly. What I would guess is only a few pounds of force. Therefore, I think that 4 lb number is probably pretty close.
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  #54  
Old 07-02-2016, 06:05 PM
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Bruce:
I would think it is closer to 150 divided by 4,resulting in about 37.5 lbs minus what ever the offset for the nut is. No engineer here so maybe one can jump in and help.
Tom
Well, strap your guitar to a table and hang 37 lbs off the end of the neck and see what happens.

(I wouldn't do that either. Without actually doing the calc, I know it's only a few lbs. It would be the sine of the angle of the neck with respect to the body. Probably a degree or two at most. Multiply that by 150 lbs. I think you'll get 3 or 4 lbs).
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  #55  
Old 07-02-2016, 06:34 PM
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This is a sine/cosine related geometry problem. If only we had paid more attention in high school geometry! The angle of divergence between the strings and the fingerboard is (or should be) less than one degree. I suspect one could multiply the string tension (nominally 150 lb) by the sine/cosine (I don't know which) of the angle of divergence and get the exact figure for deflection at 90 degrees. Perhaps it is more convoluted that that, but I think I'm close. I have seen the actual math at some point in the past, but took away only the conclusion as the part that was useful to me, and the conclusion was as I stated earlier: about 4 pounds at the nut perpendicular to the fingerboard. This is mostly useful because it allows me to use my set up bench's built in jig to add four pounds of pressure to the nut end of the fingerboard while holding the body in stasis, and then lock the whole guitar in the position so that I can do fret work with the strings off but the neck in a position closely simulating where it would be at full tension.

I am guesstimating the 4 lb using my hand to generate enough pressure to bring the fret surface to straight (counteracting the properly adjusted truss rod). For all I really know it s 3.5 or perhaps 5 lbs., but not likely outside that to bring the surface level. So, seat of the pants, I accept the figure I read what may now be 40 years ago. One nice thing about physics, and its language (math), is that 40 years may make a difference in our understanding of it, but the reality itself stays the same. Apologies to Schrödinger and his cat, of course.
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Last edited by Bruce Sexauer; 07-02-2016 at 06:44 PM.
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  #56  
Old 07-02-2016, 06:54 PM
dekutree64 dekutree64 is offline
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To me, dovetails seem like the worst of both worlds... a pain to craft, and a pain to reset. Their only advantage over bolts is the lighter weight. But of course there are also emotional aspects that can make them worth the trouble.

I like integral necks (aka Spanish heel), though they're certainly not for everyone. Just depends on how you like to construct the body. The neck gets in the way if using an outside mold, but in freeform construction, having the neck attached is a good thing. And since the outside heel takes up much of the structural role of the headblock, they can be even lighter weight than dovetails Plus you can carve interesting cutaway transitions that can't/shouldn't be done on removable necks.

Sound-wise, I don't think the neck joint makes much difference. And if it does, then integral necks are the worst, because the more sound is conducted through the neck to the body, the more you hear the after-length of the string (the part between your finger and the nut). Not good when tapping

As for neck resets being inevitable, here's a post I wrote a while back about how the guitar is naturally suited to minimizing the action rise from long term deformation, on the condition that you don't leave any weak points in the upper bout structure http://www.luthiersforum.com/forum/v...=10101&t=47103 (DennisK is me)

And aside from that, I use hide glue, ultra-thin French polish, and usually no back binding. All of which make it easier to do a heel slip neck reset if necessary.
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  #57  
Old 07-02-2016, 07:10 PM
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I have taken possession just a couple of days ago of a Rob Girdis (RIP) built D with Spanish heel construction and unplayable action. The owner no longer loves the neck (1 15/16 nut!) and so I realized I can make a whole new neck for it (has my typical 2 5/16+ bridge pin spacing) and cut a dovetail connection using the jigging I already have. I do not ordinarily take on this kind of project, but I knew and loved Rob, and the guitar's owner, who lives nearby, seems to have excellent timing and an enjoyable manner.
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  #58  
Old 07-02-2016, 07:16 PM
dekutree64 dekutree64 is offline
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Originally Posted by Bruce Sexauer View Post
I have taken possession just a couple of days ago of a Rob Girdis (RIP) built D with Spanish heel construction and unplayable action. The owner no longer loves the neck (1 15/16 nut!) and so I realized I can make a whole new neck for it (has my typical 2 5/16+ bridge pin spacing) and cut a dovetail connection using the jigging I already have. I do not ordinarily take on this kind of project, but I knew and loved Rob, and the guitar's owner, who lives nearby, seems to have excellent timing and an enjoyable manner.
What's the upper bout structure like? Any bracing between the headblock and upper transverse brace? Any soundhole bracing? UTB ends carved all the way down?

Always good to gather more data on how different structures hold up (or don't).
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  #59  
Old 07-02-2016, 08:24 PM
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Originally Posted by dekutree64 View Post
What's the upper bout structure like? Any bracing between the headblock and upper transverse brace? Any soundhole bracing? UTB ends carved all the way down?

Always good to gather more data on how different structures hold up (or don't).
The cutaway is too deep into the body, and Rob tried to run the upper transverse top brace into the side but the transfer of structure failed to be complete. The top folded in somewhat across the soundhole, though nothing actually broke. According to the owner it has been stable for perhaps 20 years, but unplayable. I expect to add some structure to the edge of the sound hole and then hope it'll stay stable for another 20 years. after I establish proper geometry with the new neck. No promises or guarantees were tendered.

I do believe the Spanish heel method is not the problem here except that it makes any adjustment very challenging, whereas either a dovetail or a hardware solution would have made things easier. The failure would have been the same in any case.

It is possible that a cleverer tech that I could slip the back, but it is fully bound with mitered purfling and since the owner wants a substantially different neck this seems the way to go. I will save Rob's head plate and put it on the new neck.

I offer some pictures, and then in order to avoid a hijack, if anyone is interested in this project I recommend my nearby blog thread is checked in on in a couple of months where if provoked (or possible not necessary), I may document the process.





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  #60  
Old 07-02-2016, 08:49 PM
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I would not mind you documenting the conversion. Always something to learn from you when you go off the beaten path, sometime even things to learn when you take the beaten path.

Did a Spanish heel on one guitar. I rather enjoyed doing it. If it were not for the reset problem I would use it again.
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